This invention relates to fluid displacement apparatus, and in particular, to fluid compressor units of the scroll type.
Scroll-type apparatus have been well known in the prior art. for example, U.S. Pat. No. 801,182 discloses a device including two scroll members each having an end plate and a spiroidal or involute spiral element. The scroll members are maintained angularly offset so that both spiral elements interfit at a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of these scroll members shifts the line contact along the spiral curved surfaces, and, therefore, changes the volume of the fluid pockets. The volume of the fluid pockets increases or decreases dependent on the direction of orbital motion. Therefore, the scroll-type apparatus is applicable to compress, expand or pump fluids. In comparison with conventional compressors of the piston-type, a scroll-type compressor has certain advantages such as fewer number of parts, and continuous compression of fluid. However, there have been several problems, primarlily sealing of the fluid pockets, wearing of the spiral elements, and outlet and inlet porting.
Although various improvements in the scroll-type compressor have been disclosed in many patents, for example, U.S. Pat. Nos. 3,884,599, 3,924,977, 3,994,633, 3,994,635 and 3,994,636, such improvements have not sufficiently resolved these and other problems.
In particular, it is desired that sealing force at the line contact be sufficiently maintained in a scroll-type compressor, because the fluid pockets are defined by the line contacts between two spiral elements which are interfitted together, and the line contacts shift along the surface of the spiral elements toward the center of spiral elements by the orbital motion of scroll member, to thereby move the fluid pockets to the center of the spiral elements with consequent reduction of volume, and compression of the fluid in the pockets. On the other hand, if the contact force between the spiral elements becomes too large in maintaining the sealing line contact, wear of spiral elements surfaces increases. In view of this, contact force of both spiral elements must be suitably maintained. However, these contact forces can not be precisely maintained because of dimensional errors in manufacturing of the spiral elements, and because to decrease the dimensional errors of spiral elements during manufacture, would complicate the manufacture of spiral elements.
Furthermore, at least one of spiral elements undertakes orbital motion to accomplish the fluid compression. Therefore, the compressor can vibrate by virtue of centrifugal force caused by this orbital motion.
These problems, that is, sealing of the fluid pockets or vibration, are not completely resolved by the above-mentioned patents.